Author Topic: Calculate exFAT checksum  (Read 1789 times)


  • Just arrived
  • *
  • Posts: 1
Calculate exFAT checksum
« on: June 09, 2016, 10:24:07 AM »

I'm want to re-calculate the checksum of a disk's VBR but I can't get the good result, when I plug it into Windows I get a fatal error and the disk isn't recognized.

I saw this topic related to ML:!topic/ml-devel/EWHU5ukyMt4

But it doesn't works... I also tried to copy/paste the related sectors directly into the script (with an hexa editor) but still the result isn't correct. Am I missing something? I copy the data from sector 0 of the VBR (offset 2048 on my disk) up to sector 10 which corresponds to 5632 bytes, calculate the checksum and don't have the right result!

Can anyone help me? Thanks!


  • Just arrived
  • *
  • Posts: 1
Re: Calculate exFAT checksum
« Reply #1 on: June 11, 2016, 06:45:51 PM »
If you are doing what you say, then you are doing it wrong.

In the first VBR record there are I think 3 bytes that are excluded ftom the calculation.

There is information on in Robert Shullich sand paper and a program on his blog at where you can extract the algorithm as well.